Cooling tower fan blade assembly having yieldable,expendable tip

ABSTRACT

A yieldable and expendable blade tip for use on the outer end of each of the blades of a cooling tower fan mounted within a fan cylinder. The tips each comprise a deformable body, preferably constructed of a synthetic resin material or the like, adapted to be mounted over the end of the blade, and releasably secured thereto by means of a binding strap and a series of fasteners extending into a respective blade. Fastener clearing slots are provided in the tip body to permit the latter to be shifted in or out longitudinally of the blade as required so that the tip may be positioned in close proximity to the inner surface of the fan cylinder. The blade tips prevent significant damage to the blades as well as the fan cylinder in case the latter is displaced by unexpectedly strong wind to an extent to permit engagement of the inner surface of the fan cylinder with the blade tips.

United States Patent [191 Holmberg et al.

[ 1 Jan. 2, 1973 [54] COOLING TOWER FAN BLADE ASSEMBLY HAVING YIELDABLE,EXPENDABLE TIP [75] Inventors: Joyce D. Holmberg, Overland Park, Kans;Earl R. Allgeyer, Raytown, Mo.

[73] Assignee: The Marley Company, Kansas City,

[22] Filed: Nov. 9, 1970 [21] Appl. No.: 88,020

[56] References Cited UNITED STATES PATENTS 2,299,920 10/1942 Moore..26l/D1G. 11 3,544,231 1 12/1970 Zerlauth.. ..415/174 3,079,128 2/1963Burge ..415/174 885,032 4/1908 De Ferranti ..415/172 930,907 8/1909Westinghouse "415/174 3,199,836 8/1965 Moyer ..415/174 2,447,957 8/1948Moore ..415/174 Primary Examiner-Tim R. Miles Assistant Examiner-StevenH. Markowitz Attorney-Schmidt, Johnson, Hovey & Williams [5 7 ABSTRACT Ayieldable and expendable blade tip for use on the outer end of each ofthe blades of a cooling tower fan mounted within a fan cylinder. Thetips each comprise a deformable body, preferably constructed of asynthetic resin material or the like, adapted to be mounted over the endof the blade, and releasably secured thereto by means of a binding strapand a series of fasteners extending into a respective blade. Fastenerclearing slots are provided in the tip body to permit the latter to beshifted in or out longitudinally of the blade as required so that thetip may be positioned in close proximity to the inner surface of the fancylinder. The blade tips prevent significant damage to the blades aswell as the fan cylinder in case the latter is displaced by unexpectedlystrong wind to an extent to permit engagement of the inner surface ofthe fan cylinder with the blade tips.

16 Claims, 8 Drawing Figures PATENTEDJM ems 3.708.155

' sum 1 or 2 //v VEN 75025..

flTTORNEYS.

[Joyce 0. Ha/mbe/g COOLING TOWER FAN BLADE ASSEMBLY HAVING YIELDABLE,EXPENDABLE TIP This invention relates to water cooling towers andparticularly to improved fan structure therefor wherein deformable,synthetic resin tips are provided on the fan blades so that in the eventof engagement of the tips with the fan cylinder normally surrounding thefan blades, the tips deform as required to prevent complete destructionof the cylinder or the blades themselves.

Induced draft water cooling towers are conventionally provided with afan cylinder surrounding each of the draft fans. These cylindersnormally have a venturi type constriction at a point adjacent to and indirect alignment with the plane of rotation of the fan. The innersurface of the cylinder is of smooth configuration and aerodynamicallydesigned with streamlined tapering of the inner cylinder wall leading upto and away from the point of maximum constriction.

The streamlining of the inner surface of the cylinder wall is desirablein order to decrease friction and air drag and the venturi constrictionis provided to assure maximum air flow through the tower as well asmaximum exhaust air speed out of the tower. Maximum hot air exhaustvelocity is required to prevent cycling of the hot air expelled backthrough the cool air inlet of the tower which would lower the coolingefficiency of the tower.

The fans for large capacity cooling towers often are 28 feet in diameteror more to move sufficient air to effectively cool the extremely largequantities of water handled by these towers. Manifestly, blades for fansof this diameter must be of sufficient strength to not only withstandcantilever mounting thereof but also resist significant deflectionduring operation. Large cast metal or glass fiber reinforced syntheticresin members of relatively high weight have been found to be the mostsatisfactory materials for constructing such fan blades.

The provision of a venturi type fan cylinder for a cooling tower and theadvantages derived therefrom is of common knowledge to those skilled inthe cooling tower field. In this connection, it is known that the fanblades must be positioned extremely close to the inner surfaces of thecylinder wall in order to take full advantage of the inherent propertiesof the venturi,

Problems arise, however, when high winds or other factors cause the fancylinder to bend or flex. The bending or deforming of the fan cylindercan permit the fan blades to strike the inner surface of a cylinder walland thus cause severe damage to the cylinder wall, fan blades,transmission, and supporting structure. This damage is not onlyexpensive to repair but valuable operational time is lost as well. Evenif the damage is slight with only a portion of a fan blade beingdamaged, the repair or replacement of the blade still amounts to asignificantly large loss of operational time. In addition, the amount ofwork output required to repair or replace the blade coupled with thecost thereof makes it desirable to take precautionary steps againstengagement of the blades with the fan cylinder. It can be appreciated inthis respect that the usual practice of shortening the blades is not areally satisfactory solution to the problem since the effective volumeof air capable of being moved by the fan and the effectiveness of theventuri would both be diminished.

Therefore, it is desirable to have a blade tip which will, upon strikingthe inner surface of a cylinder wall, cause as little damage as possibleto the cylinder wall and other related fan assembly parts and which isalso capable of being quickly and easily replaced with as littleoperational time lost as possible. Accordingly, it is the primary objectof this invention to provide a yielda ble fan blade tip for a coolingtower fan located within a fan cylinder which will substantiallyeliminate cylinder wall scoring and other types of damage to fanassembly parts resulting from cylinder wall deflection or otherconditions which cause the fan blade to strike the inner surface of thecylinder wall.

It is another important object of this invention to provide such a fanblade tip which will permit the blade to be positioned as closely aspossible to the cylinder wall in order to assure mostefficientutilization of the fan and the venturi as well.

It is still another important object of this invention to provide such afan blade tip which may be quickly and conveniently installed on andremoved from the blade body when necessary for replacement or repairpurposes.

A further important object of the invention is to provide a deflectablefan blade tip of the characteristics described which especially lendsitself to fabrication from a synthetic resin by conventional extrusionor injection molding techniques thereby making it possible to producethe tips at a reasonable unit cost and to reproduce the same as neededwithout additional tooling costs.

Still other important objects of the invention will be made clear orbecome apparent to those skilled in the art from the drawings, and thedescription of a preferred embodiment of the invention as set forthhereinafter.

In the drawings:

FIG. 1 is a fragmentary elevational view of a cooling tower having a fanassembly equipped with a cupshaped blade tip of preferred constructionand embodying the principles of our invention, parts of the tower beingpartially broken away and shown in vertical cross section to revealdetails of construction;

FIG. 2 is an enlarged perspective view of the blade tip of FIG. 1 shownremovably mounted in place on the outer portion of a typical fan blade;

FIG. 3 is an enlarged, fragmentary, end elevational view of the outerextremity of the blade tip as shown in FIG. 4 is an enlarged,fragmentary, plan view, of the blade tip as illustrated in FIG. 3 withportions of the blade tip broken away to reveal details of construction;

FIG. 5 is an end elevational view of a modified form of the inventioncomprising a tubular blade tip adapted to be constructed by extrusiontechniques;

FIG. 6 is a plan view of the blade tip illustrated in FIG. 8 is a planview of the blade tip shown in FIG. 7 and illustrating the modified tipmounted in place on a fan blade with certain parts thereof also beingbroken away and in section.

. The induced draft, crossflow water cooling tower illustrated in FIG. 1is generally designated by the numeral 10. Cooling tower 10conventionally includes a fan assembly 12 mounted in the upper frameworkthereof above divider 28 separating opposed fill assemblies 26 one fromthe other. Hot water distribution basins 27 overlie respective fillassemblies and deliver hot water thereto for eventual delivery to coldwater basin 30 underlying the casing 32 of the tower after cooling ofthe water by evaporation of a part thereof. Fan assembly 12 is made upof a gear unit 18 operably driven through shaft 20 by electric motor 22coupled thereto and joined to the series of radially extending blades 14for rotating the latter in a horizontal plane at a present speed. Eachof the blades 14 is provided with a removable, expendable tip 16 on theouter end thereof proximal to the smooth inner surface 240 of fancylinder 24 located in surrounding relationship to fan assembly 12.

In the preferred form of the invention detailed in FIGS. 24, each of theblade tips 16 is constructed of yieldable synthetic resin material andmolded to present a hollow cup-shaped body configured to partiallytelescope over the outer end of the blade 14. Tips 16 are each securedto a corresponding blade 14 by an elongated binding strap 34 andfasteners 36. The outer, elongated, longitudinally curved, transverselystraight end wall 38 of each blade tip 16 is adapted to lie alongsidethe inner surface of the fan cylinder wall 24 and is provided with aseries of water drain holes 40 to prevent accumulation of water in theinterior of the blade tip 16. The blade tips 16 have a series of spacedslots 42 provided therein around the open end 46 of each blade tip 16remote from end wall 38.

Referring to FIG. 1, illustrating the relative relationship between thevarious components of the cooling tower, it is to be seen that the fanassembly 12 is mounted within the fan cylinder 24 with the plane ofrotation of the blades 14 in substantial alignment with the plane ofmaximum venturi restriction through the points on the inner surface ofthe cylinder wall indicated by the numerals 44. The fact that the outerend extremity 38 of the blade tip 16 can be easily positioned in closeproximity to the inner surface of the cylinder wall 24 is readilyapparent. It also can be appreciated that any deflection or deformationof the fan cylinder 24 by wind currents or otherwise will cause the tip16 to come'in contact with the inner surface of the cylinder wall 24.However, because the blade tip 16 is constructed of yieldable syntheticresin material or the like, the blade tip 16 will bend or shred whenstriking the cylinder wall 24 thereby allowing the cylinder wall 24 toescape any scoring or structural damage. The bending and shredding ofthe blade tip 16 also prevents damage to the gear unit 18 or drive shaft20 by eliminating the shock of the blade tip 16 striking the cylinderwall and the momentary binding of the blade tip 16 on the cylinder wall24 which would normally be transmitted through the drive line of the fanassembly if a conventional blade and blade tip were used. The onlydamage which can occur then, resulting from the blade tip 16 strikingthe inner cylinder wall 24 is tothe blade tip 16 itself; however, sincethe blade tip 16 may be removed and discarded, a new blade tip 16 mayreadily be mounted on the blade 14 in place of the damaged member.

The blade tip 16 of preferred construction as shown in FIGS. 2-4 isconstructed generally in the form of a flattened cup with elongatedsidewalls defining an opening 46 at the end thereof remote from the endwall 38. This construction is desirable for two reasons. First, itprovides a convenient method of mounting the blade tip 16 on the blade14 by slipping the blade tip 16 over the terminal end 48 of the blade 14and along a portion of the latter with the terminal end 48 beingcomplementally received within the open extremity 46 of blade tip 16 andpartially within the interior of the latter. Secondly, the hollowconstruction of blade tip 16 reduces the rigidity thereof thus lesseningthe possibility of cylinder wall damage upon engagement of the tipmember with the inner surface of the fan cylinder. The potential problempresented within member 16 of moisture accumulating within the hollowchamber 50 is solved by the provision of drain holes 40 through the endwall 38 allowing entrapped moisture to escape therethrough.

The blade tip 16 is also provided with an external configuration similarto that of blade 14 in order to maintain the aerodynamic properties ofblade 14 throughout the entire length of the blade 14 and tip 16. Itshould be noted that the end wall 38 of the blade tip 16 islongitudinally arcuate in the direction of rotation of blade 14 topermit disposition of the blade tip 16 in close proximity to the innersurface of the cylinder wall 24. The end wall 38 is curved across thewidth thereof as can be observed in FIG. 4 but is straight or flat in atransverse direction between the top and bottom surfaces thereof inorder to allow a greater amount of surface area of end wall 38 to bedisposed in close proximity to the inner. surface of the cylinder 24,thereby providing increased volumetric efficiency and venturiutilization.

In use, the blade tip 16 is mounted on the blade 14in the mannerpreviously described by slipping the blade tip 16 over a portion of theblade 14 with the terminal end 48 of the blade 14 being received withinthe open extremity 46 of the blade tip 16. Binding strap 34 is thenpositioned around the blade tip 16 in an overlying relationship thereto,as illustrated in FIG. 4. The fasteners 36 are inserted through openings(not shown) provided in the binding strap 34 and aligned, elongatedslots 42 in the blade tip 16, and are finally received within threadedholes 52 provided in the blade 14 adjacent the terminal end 46. Theblade tip 16 may now be adjusted inward and outward in relation to theblade 14 by virtue of elongated slots 42 for proper positioning of theblade tip 16 relative to the inner surface of the cylinder wall 24.

After the blade tip has been positioned properly relative to thecylinder wall 24, the fasteners 36 are tightened down to secure theblade tip 16 to the blade 14. When it is necessary to remove the bladetip 16 for replacement purposes the fasteners 36 and binding strap 34may readily be removed and the blade tip 16 then slipped off of the end46 of the blade 14.

An alternate blade tip broadly designated 116 is shown in FIGS. 5 and 6of the drawings. Tip 116 comprising a tubular sleeve 116a is of uniformcross-sectional configuration permitting extrusion thereof fromsynthetic resin material. It is tobe noted though that thecross-sectional shape of tip 1 16 is the same as tip 16 and the internalpassageway 116b therethrough is of a size to accommodate blade 14 sothat the tubular sleeve may be complementally fitted over the outer endof the blade and elongated slots 142 in sleeve 116a functionin themanner as slots 42 for adjustment of tip 116 longitudinally of blade 14as desired while fasteners 136 and strap 134 serve in a fashion similarto components 34 and 36 to releasably secure tip 116 to blade 14.

Blocks 152 between and secured to the opposed major inner surfaces ofsleeve 116a reinforce the end margins of the tip body and assure thatthe tip retains its shape during rotation of the fan blade on which thetip 1 16 is mounted. Water cannot collect in the interior passage 1l6bof sleeve 116a because spacers 152 do not block the outer open end ofthe tip body.

Another alternate blade tip 216 illustrated in FIGS. 7 and 8 is adaptedto be injection molded from synthetic resin material and includes asolid main body portion 216a conforming to the configuration of tip 16and the outer shape of blade 14 and has a cup-shaped cavity 216!) moldedin one end thereof for complementally receiving the outer end of blade14 in telescopic relationship thereto. Elongated openings 242 in bodyportion 216a aligned with cavity 216k permit adjustment of thedisposition of tip 216 relative to blade 14 longitudinally of the latteras previously described with reference to tip 16 and 116 while fastenersand a strap (not shown) the same as fasteners 34 and 134 as well as astrap equivalent to straps 34 and 134 are also provided for releasablyafiixing tip 216 to blade 14. j

A series of individual, outwardly projecting fingers 2160 are integralwith body 216a and are of shape to also conform with the adjacentcross-sectional shape of body portion 216a with adjacent fingers beingprovided with mutually cooperable tongue and groove surfaces 216d and216a intermediate opposed major faces of the tip which serve tointerconnect proximal fingers 216a but'do not interfere with relativelongitudinal shifting thereof as illustrated in FIG. 8. I

Thus, upon engagement of fingers 2160 with the inner fan of the fan'cylinder, the fingers deflect as shown and do not tear up the cylinderwall as would be a yieldable, expendable tip member carried byeach ofthe blades at the outermost extremity thereof adjacent the inner surfaceof said cylinder and interposed between the latter and a respectiveblade,

said tip members having opposed, curved sidewalls of generallycomplemental shape to said sidewalls of a corresponding blade andprovided with leading and trailing edges which terminate in proximalrelationship to adjacent edges of a respective blade, j j j meansreleasably securing each tip member to a corresponding blade to permitreplacement-thereof as required without the necessity of replacing theen tire blade.

2. The invention of claim 1, wherein each of said tip members isprovided with spaced sidewalls and an end wall defining a cavity forcomplementally receiving the terminal end of a respective blade.

3. The invention of claim 2, "wherein each of the blades istelescopically received within a corresponding tip member with the outerend of each blade disposed in spaced relationship from the end wall ofthe respective tip member.

4. The invention of claim 3, wherein the outermost end of each tipmember remote from the blade on which it is mounted being longitudinallyarcuate in the direction of rotation thereof to permit disposition ofthe tip member in close proximity to the inner surface of the fancylinder.

5. The invention of claim 2, wherein is provided a binding strap in atleast partial circumscribing relationship to each tip memberandoverlying the extremity of the blade telescoped into the cavitythereof, and said releasably securing means comprises a series offasteners extending through the strap and said tip member into theblade. 1

6. The invention of claim 5, wherein each of said tip members isprovided with an elongated slot therein receiving a respective fastener,said slots being of greatest length in a direction extendinglongitudinally of the blade to permit selective adjustmentof the tip thecase with a solid fan blade tip. Unless the tip 216 engages the cylinderwall with an unusually great degree of force, the fingers 216a cansimply be returned to their normal linear configuration and thus makingit unnecessary to replace 216. Oftentimes, this is accomplishedautomatically, during rotation of the fan due to the centrifugal forceon tip 216.

Having thus described the invention, what isclaimed as new and desiredto be secured by Letters Patent is:

1. In a water cooling tower having a fan assembly provided with a seriesof radially extending blades, and a fan cylinder in surroundingrelationship to said assembly, the outermost end extremity of each bladeproximal to the fan cylinder being provided with transversely curved andopposed sidewalls, the combination therewith of:

member toward and away from the inner surface of the fan cylinder.

7. The invention of claim 3, wherein said end wall of each tip member isprovided with at least one opening therein to prevent accumulation ofwater in the cavity of a respective tip member.

8. The invention of claim 1;,wherein each of'said tip members comprisesa cup-shaped element having rela tively thin, readily deformable wallsfabricated of synthetic resin material. t

9. The invention of claim 1, wherein the transversely arcuate sidewallsof each tip are configured to complementally engage opposed sides of acorresponding blade. 1

10. The invention of claim 9, wherein the outermost end extremity ofeach blade proximal to the fan cylinder has curved edges connectingrespective opposed extremities of said sidewalls and thetip membermounted thereon has opposed arcuate edge walls connecting respectiveopposed tip member sidewalls configured to complementally engage opposededges of the blade;said outermost end of each tip member remote from theblade in which it is mounted being transversely straight in a directionperpendicular to the direction of rotation thereof to allow a greateramount of surface area of said outermost end to be disposed in closeproximity to the inner surface of the fan cylinder.

11. The invention of claim 1, wherein each of said tip members comprisesa tubular sleeve having walls presenting a central passage therethroughof a configuration to complementally receive the outer end of a fanblade therein for telescopic mounting of the sleeve on the blade, andspacer means within the outer open end sleeve being of uniform thicknessto permit extrusion of the sleeve.

1;. The invention of claim 1, wherein each of said tip members isprovided with a body portion provided with means thereon for mountingthe body portion of the outer end of a corresponding blade, and a seriesof deflectable fingers joined to the body portion and extendingoutwardly therefrom in a direction toward the fan cylinder when the tipmember is mounted on a corresponding blade.

14. The invention of claim 13, wherein said fingers are parallel,disposed in side-by-side, interengaging relationship and are integralwith said body portion.

15. The invention of claim 14, wherein adjacent fingers are providedwith mutually cooperable, slidably interlocked tongue and grooveportions which prevent movement of the fingers away from each other butdo not interfere with relative longitudinal movement of the fingers inthe event of engagement of the fingers with said fan cylinder.

16. The invention of claim 14, wherein the outer configuration of thebody portion and said fingers is substantially complemental to thecross-sectional shape of the blade and said body portion is providedwith a cavity in the extremity thereof remote from said blade forcomplementally receiving the outer end thereof.

1. In a water cooling tower having a fan assembly provided with a seriesof radially extending blades, and a fan cylinder in surroundingrelationship to said assembly, the outermost end extremity of each bladeproximal to the fan cylinder being provided with transversely curved andopposed sidewalls, the combination therewith of: a yieldable, expendabletip member carried by each of the blades at the outermost extremitythereof adjacent the inner surface of said cylinder and interposedbetween the latter and a respective blade, said tip members havingopposed, curved sidewalls of generally complemental shape to saidsidewalls of a corresponding blade and provided with leading andtrailing edges which terminate in proximal relationship to adjacentedges of a respective blade, means releasably securing each tip memberto a corresponding blade to permit replacement-thereof as requiredwithout the necessity of replacing the entire blade.
 2. The invention ofclaim 1, wherein each of said tip members is provided with spacedsidewalls and an end wall defining a cavity for complementally receivingthe terminal end of a respective blade.
 3. The invention of claim 2,wherein each of the blades is telescopically received within acorresponding tip member with the outer end of each blade disposed inspaced relationship from the end wall of the respective tip member. 4.The invention of claim 3, wherein the outermost end of each tip memberremote from the blade on which it is mounted being longitudinallyarcuate in the direction of rotation thereof to permit disposition ofthe tip member in close proximity to the inner surface of the fancylinder.
 5. The invention of claim 2, wherein is provided a bindingstrap in at least partial circumscribing relationship to each tip memberand overlying the extremity of the blade telescoped into the cavitythereof, and said releAsably securing means comprises a series offasteners extending through the strap and said tip member into theblade.
 6. The invention of claim 5, wherein each of said tip members isprovided with an elongated slot therein receiving a respective fastener,said slots being of greatest length in a direction extendinglongitudinally of the blade to permit selective adjustment of the tipmember toward and away from the inner surface of the fan cylinder. 7.The invention of claim 3, wherein said end wall of each tip member isprovided with at least one opening therein to prevent accumulation ofwater in the cavity of a respective tip member.
 8. The invention ofclaim 1, wherein each of said tip members comprises a cup-shaped elementhaving relatively thin, readily deformable walls fabricated of syntheticresin material.
 9. The invention of claim 1, wherein the transverselyarcuate sidewalls of each tip are configured to complementally engageopposed sides of a corresponding blade.
 10. The invention of claim 9,wherein the outermost end extremity of each blade proximal to the fancylinder has curved edges connecting respective opposed extremities ofsaid sidewalls and the tip member mounted thereon has opposed arcuateedge walls connecting respective opposed tip member sidewalls configuredto complementally engage opposed edges of the blade; said outermost endof each tip member remote from the blade in which it is mounted beingtransversely straight in a direction perpendicular to the direction ofrotation thereof to allow a greater amount of surface area of saidoutermost end to be disposed in close proximity to the inner surface ofthe fan cylinder.
 11. The invention of claim 1, wherein each of said tipmembers comprises a tubular sleeve having walls presenting a centralpassage therethrough of a configuration to complementally receive theouter end of a fan blade therein for telescopic mounting of the sleeveon the blade, and spacer means within the outer open end of the sleevefor supporting the outer extremities of the walls thereof remote fromthe blade, said spacer means being in only partial blocking relationshipto the outer end of the sleeve to prevent accumulation of water in saidpassage.
 12. The invention of claim 11, wherein the outercross-sectional configuration of said sleeve transversely thereof is ofthe same shape as said blade in a transverse direction at the areathereof adapted to be telescopically received in the passage, said wallsof the sleeve being of uniform thickness to permit extrusion of thesleeve.
 13. The invention of claim 1, wherein each of said tip membersis provided with a body portion provided with means thereon for mountingthe body portion of the outer end of a corresponding blade, and a seriesof deflectable fingers joined to the body portion and extendingoutwardly therefrom in a direction toward the fan cylinder when the tipmember is mounted on a corresponding blade.
 14. The invention of claim13, wherein said fingers are parallel, disposed in side-by-side,interengaging relationship and are integral with said body portion. 15.The invention of claim 14, wherein adjacent fingers are provided withmutually cooperable, slidably interlocked tongue and groove portionswhich prevent movement of the fingers away from each other but do notinterfere with relative longitudinal movement of the fingers in theevent of engagement of the fingers with said fan cylinder.
 16. Theinvention of claim 14, wherein the outer configuration of the bodyportion and said fingers is substantially complemental to thecross-sectional shape of the blade and said body portion is providedwith a cavity in the extremity thereof remote from said blade forcomplementally receiving the outer end thereof.